Synthesis of Functionalized 1H-Indenes and Benzofulvenes through lodocyclization of o-(Alkynyl)styrenes

A convenient method for the preparation of synthetically useful 3-iodoindene derivatives has been developed. This protocol, based on the 5-endo iodocyclization reaction of o-(alkynyl)styrenes, represents one of the scarce examples of haloc-yclizations using olefins as nucleophilic counterparts and allows the synthesis of both 3-iodo-1H-indenes (from beta-alkyl-beta-alkyl/aryl-o-(allcynyl)styrenes) and 3-iodobenzofulvenes (from beta,beta-diaryl-o-(alkynyl)styrenes) in good yields under mild reaction conditions. In addition, related alkoxyiodocyclization processes are described, which are particularly interesting in their intramolecular version because they allow the synthesis of heteropolycyclic structures containing the indene core. Finally, the usefulness of the prepared 3-iodoindenes has been demonstrated by the synthesis of several polysubstituted indene derivatives through conventional palladium-catalyzed cross-coupling reactions and iodine lithium exchange processes.